Tsunami warnings were issued across parts of the Pacific on Wednesday following an earthquake of 8.7 size at Russia’s Far East.
Here are important facts about tsunamis and the injury they can cause:
Shock of water
A tsunami is a shock of water that spreads through the sea, usually triggered by a strong earthquake under the seabed.
The sudden, violent movement of the earth’s crust can push up or run down a section of the seabed, with the itchy displacement large amounts of water moving like waves.
Tsunamis radiate in all directions from their source and can cover huge distances, sometimes with the speed of a jet.
They are a rare phenomenon, but can create dangerously powerful streams and cause deadly floods in coastal areas.
Other causes
Large earthquakes are the most important driving force for tsunamis, but the phenomenon can also be triggered by other cataclysmic geographical events, such as volcanic eruptions and landslides.
In 1883, a volcano crushed the Pacific Island Krakatoa, causing an explosion that could be heard 4,500 kilometers (2,800 miles) away, followed by a tsunami that killed about 30,000 people.
Large storms or a meteorite that falls into the sea can also be powerful enough to cause a tsunami, according to the US National Oceanic and Atmospheric Administration.
‘Harbor Wave’
The word “tsunami” comes from the Japanese words for “port” and “wave”.
Tsunamis are sometimes referred to as “tidal waves”, but experts say this is inaccurate because they are not related to tides.
At their generation point, tsunamis have a relatively small wave height with tops far apart.
As the waves approach the coast, they are compressed by the shelves on the seabed, reduces the distance between peaks and increases enormous height.
When they hit the coast, tsunami waves can beat repeatedly over several hours or even days.
Roman historian
To those on the coast, the first sign of something wrong may be the withdrawal of the sea, which is followed by the arrival of large waves.
“The sea was driven back, and its waters floated away to such an extent that the deep sea was laid just, and many kinds of sea creatures could be seen,” wrote Roman author Ammianus Marcellinus of a tsunami that hit Alexandria in 365 AD.
“Huge plenty of water floated back when it was at least expected, and now overwhelmed and killed many thousands of people … Some good ships were thrown by the waves’ rage on the rooftops.”
How much damage?
Several factors determine the height and destructiveness of a tsunami.
They include the size of the earthquake, the amount of displaced water, the topography on the seabed and whether there are natural obstacles that dampen the shock.
The Pacific is especially inclined to earthquakes and therefore for tsunamis, but for millennia tsunamis have occurred in many parts of the world.
The Tsunami in December 2004 in the Indian Ocean was caused by an earthquake of 9.1 from the Indonesian island of Sumatra.
It released energy equivalent to 23,000 of the nuclear bombs fell on Hiroshima, according to US Geological Survey (USGS). About 220,000 people in 11 nations were killed, many of them thousands of miles from the episent.
